FMS leads to lean manufacturing: six HMCs change part flow.

By using lean initiatives along with a Flexible Manufacturing System (FMS), Gardner Denver, Sedalia, MO, has reduced cycle times for producing blower components by 75 percent.

Gardner Denver manufactures compressors, blowers, and pumps for industrial applications and pumps used in oil and natural gas production, well servicing, drilling, and water-jetting systems.

Before adding the FMS and single-part flow, Gardner Denver used a batch system to produce parts, explains manufacturing engineering manager Art Townsend. "We were basically a batch manufacturing setup with grand goals and a lot of old equipment and processes. Our desire was to put in the right capital investment and processes to take us up a notch in the building and manufacture of our products. The company always wanted to do an FMS, but more importantly, we wanted to flow our products. At the start, we had no lean manufacturing program, but I had experience with lean manufacturing from my previous position, and was brought in to redevelop the way Gardner Denver produced parts."

Along with adding an FMS, Townsend said that a manufacturing engineering group needed developing to tackle tool design, NC programming, work holding, and other production issues. "We had to find engineer that had knowledge of these processes and the rest we had to teach Director of Manufacturing Mike Clements, who was the plant manager at one time, was the person who wanted to modernize the whole plant, including the blower and compressor lines. He focused on blower components, because there was more product volume there, and it was a quicker payback. We also had a lot of vendors manufacturing these parts, and we felt we could produce them on the inside. If we were going to put in new machines, there was no point in putting in standalone ones, because we already had them. So, we decided to change everything," Townsend explains.

Part flow capacity

Townsend says it's easier to manage parts coming off the FMS because they can easily do smaller batch sizes, and it's possible to do one-off parts, as well as run unattended. Another critical aspect of the FMS is the assembly line that allows parts to flow from machining right into the assembly process. Parts travel from machining to deburring then flow into the assembly area and finally to product testing and shipment packaging.

All this was being developed along with lean initiatives that changed the way Gardner Denver manufactured products at this facility. "If we had machines scattered all over the plant, we couldn't create product flow and it wouldn't be a lean environment," Townsend says.

In 1998, the company ordered three Toyoda FA630 HMCs for the FMS. Later they ordered three more for a total of six Toyoda 630 mm pallet machines.

Currently there are 32 pallets with three load/unload stations where the operator does a final QC check as the parts are pulled off the pallets. Pallets are shared with other Toyoda HMC standalone machines and more machines can be added with the current automated-guidance system that moves the pallets from a linear-pallet pool to the machine. Parts are primarily gray iron with steel used for blower rotors. Brass housings are used for some oil-free screw compressor applications.

The smallest blower falls within a 12" to 18" cube, and the largest blower "you can walk inside," says Townsend. "Our smallest rotor is about 74 mm, while our largest one is roughly 350 mm," he adds.

On the FMS, parts that are about a meter cubed in size can be produced. "Typically on a 630-mm pallet machine, you'll end up with about a 1.9 m cube. We needed a little bit more part size capability, and that was one reason why we went with Toyoda over other manufacturers because, in that pallet size, they had a little more travel on their axes," says Townsend.

"Typically when you put in an FMS, you're always concerned about the automation side, software, controls, material handling," says Townsend.

At Gardner Denver, FMS pallets are identified through a side tag that is read by the remote-guided vehicle using an infrared light. The FMS knows what part it has and which program to download for machining. For their workholding fixtures, Townsend says they designed their own, but Toyoda put an application engineer at their disposal when they first started up the FMS. The engineer did some of the first part programming because the operators were unfamiliar with the new controls. Today they use Espirit for part programming over an Ethernet connection.

Because of the problems with dust when cutting ductile iron, Townsend says they decided to use cutting fluid. "Once we started using cutting fluid, it cut the dust down considerably," he adds.

Tooling issues

Tooling was a new issue with the FMS. "Our old equipment didn't have the RPMs to run some of the newer tools that we wanted to use. We couldn't use some of the new cutting materials, and mills, and we couldn't handle faster surface feeds. Once we got new machines with their greater capabilities and coolant, we had to add other new tools. Our tooling procedure was almost as big or bigger than the machine tool selection process," says Townsend.

When the FMS was delivered it was equipped with either 12,000 or 14,000-rpm spindles. Townsend says they replaced those with 6,000 rpm ones to gain a better torque curve. "I was only cutting cast iron, so I really didn't need high rpms," he adds.

Lead man on the FMS, Dale Trolinger, adds that the FMS has dramatically cut down on part-cycle times. He also says when they need a part quickly that isn't already in the FMS, if the fixture is already in the buffers and the tooling is available, they can easily call up the pallet, and let it run.

For tooling, Townsend adds, "We had a plethora of tooling such as drills, taps, boring bars, and face mills that were new. We tried silicon nitride and diamond coatings, but we ended up getting back to carbide for the most part. However, we have all types of new tooling we're trying out."

Townsend says they've also tried ceramic tooling, but it required dry cutting. They did try some ceramic tooling with coolant, but with limited success and he reported it wasn't worth the cost for this application.

Tool life was another issue they looked at. Townsend says, "That's still another work in progress because we had no way to measure tool life before the FMS. I don't have a base to say yes, it's better now, but I think it is. Even working with the FMS, we've seen our tool life improve, but I don't really have a baseline for a good comparison. So we try to maximize our feeds and speeds."

To develop a baseline to change-out tools, Trolinger remarks, "We have 120 tools residing on each machine with six machines giving us 720 different possible tool combinations. We started all the tools at a 60-minute duration. Then we'd inspect them and see if there was any kind of wear. If not, then we'd move the time up. We've got several of them already tested and can tell what the life is. Of course, it's just a reference, but it does help a lot."

The FMS cell controller also monitors tool life over time. Trolinger adds, "It tells you whenever a tool gets out of the allotted time. You can set a maximum amount of time or a certain limit. Once the tool gets to the maximum time it gives you a warning. Then once it gets to the limit it stops the machine."

In the case of a catastrophic failure such as a large drill breaking, Trolinger says a touch sensor will stop the machine. The sensor is an electric magnet wrapped around the spindle. Any time the tool touches the part the magnet engages. If it doesn't touch within a certain distance, it alarms out and indicates a broken tool.

For boring bars and mills, Toyoda uses a horsepower monitor. If it gets over a certain horsepower the machine stops. To activate it, the teach mode is turned on in the controller. It runs the tool and the load can be set 10 percent over the highest horsepower it uses for the operation. As the tool dulls and goes over your high programmed limit, the machine will either slow the tool down as it's running or it will stop the machine.

Toyoda's FMS made some dramatic changes at Gardner Denver. Before the system, a part might be fixtured on up to seven different machines for production. Now the company's goal is to do complete machining with one fixturing and then on to assembly.

Once the part is taken off one of the load/unload stations, it's checked for critical dimensions. A CMM checks parts for feature comparison and reference such as the distance between rotor bores. But Townsend says they rely on the machining process itself, and the quality constraints built into the Toyoda machines such as tool probes, tool monitoring, and broken-tool detection to keep their quality consistent.

After inspection, the part is deburred, and then kitted for assembly. "Our goal is to develop a one-piece flow. However, it's not always economically the right thing to do. Being able to do one-off is a good thing. The fact that you can do one-off doesn't mean that you should. I can do small lot sizes, and that works out better. If you do one-off all the time, that tends towards chaos, as opposed to flow," says Townsend. Toyoda Machinery USA, www.rsleads.com/309tp-194